1. Field of the Invention
The invention relates to electrical components. In particular, the invention relates to radio-frequency components and their assembly.
2. Related Art
The information contained in this section relates to the background of the art of the present invention without any admission as to whether or not it legally constitutes prior art.
Various methods have been employed for assembling of components for spacecraft and other applications. For example, reference may be made to the following U.S. patents:
U.S. Pat. NO.INVENTORISSUE DATE4,397,434FarnhamAug. 9, 19834,875,795AndersonOct. 24, 19895,535,295MatsumotoJul. 9, 19965,724,051Mailandt et al.Mar. 3, 19985,803,402Krumweide et al.Sept. 8, 19985,849,204MatsumotoDec. 15, 19986,046,704LopezApr. 4, 20006,064,969HaskinsMay 16, 20006,148,740Jackel et al.Nov. 21, 20006,307,451 B1Saitoh et al.Oct. 23, 2001
Electrical components such as feedhorns, wave guides, adapters and others have been used in spacecraft and other applications. Feedhorns, for example, are used to obtain and direct radio frequency (RF) energy reflected from a satellite dish. Feedhorns used in space require an unusual combination of low weight, structural stiffness, and thermal stability, which are difficult to achieve simultaneously. Certain feedhorns are generally made of a metal that is machined. For example, some early structures were fabricated from metals such as aluminum or light alloys resulting in a heavy structure. Since the overall weight of a spacecraft is constrained by the payload capabilities of a given launch vehicle, a relatively heavy structure resulted in a reduction of onboard equipment and instrumentation that could be included in the satellite. The emphasis therefore is to make future spacecraft lighter, faster and less expensive.
It is desirable that the feedhorn have sufficient structural strength and stiffness because the satellite must be able to withstand forces imparted during launch without permanent deformation. A feedhorn lacking sufficient strength and stiffness, even if it is low weight, may not survive the launch process. Thermal stability is another important parameter in feedhorn design because the feedhorn is often exposed to extremes of temperature caused by the difference in heat load between the sunlit side and the shadow side of the spacecraft. The materials and construction methods used to construct the feedhorn need be capable of providing a foundation that will not bend or distort under these different temperature loadings. Minuscule distortions sufficient to negatively affect critical alignment can occur that may render a scientific payload inoperable. Moreover, the trend to further lighten payloads by fabricating much of the payload hardware from composite materials has increased the need to achieve a better thermal match between the payload hardware and the spacecraft.
Traditional metallic feedhorns are machined from a solid block of metal. These are heavy in weight as compared to composite material feedhorns and are difficult to fully optimize due to limitations of machining thin walls. Thus, previously manufactured composite feedhorns have been formed from individual piece parts held in-place with assembly tooling that are then adhesively bonded together. The elements are generally held together using the tool or fixture during the bonding process. The bonding process must be performed with the tool generally obstructing easy access to some areas, resulting in a cumbersome and expensive bonding and manufacturing process. The tools used to assemble the feedhorn can be expensive and even obtrusive to regions within the feedhorn where the tooling exists, which can make bonding the assembly together awkward and time consuming.
U.S. Pat. No. 5,803,402, to Krumweide, discloses a method of assembling a spacecraft framework using structural components held together with little or no tools or fixtures required to hold the components during the bonding process. The components may then be bonded together in a rigid configuration.
There is a need for a low cost method of producing spacecraft feedhorns and other electrical components that are strong, rigid, lightweight, and thermally stable to meet the rigors of outer space. These types of components generally require close tolerances, as may be the case for RF components such as antennae. For example, close tolerances in the surface configuration and shape may be critical in these components.